Can a Multivitamin Deter Cancer?

Some researchers say yes, while others say no

Could you lessen your chance of getting cancer by taking a multivitamin every day? Most investigations of that question have yielded “decidedly mixed results,” according to a recent article in the New York Times.

Boston researchers announced last fall that one of the largest long-term clinical trials of multivitamins in the United States, encompassing 14,000 male physicians ages 50 and older and lasting a decade, found that taking a combination of essential vitamins and minerals on a daily basis decreased the incidence of cancer by 8 percent, compared with a placebo pill. But some earlier trials using high doses of nutrients thought to be cancer fighters actually drove up cancer rates instead of reducing them.

“There’s a mystique about vitamins, that vitamins are some type of magical ingredient,” said David Schardt, senior nutritionist for the Center for Science in the Public Interest, an advocacy group in Washington, D.C. “There is a kernel of truth in that, because vitamins are essential to life. But that people will live longer or healthier lives if they take vitamins or eat foods fortified with vitamins—that’s difficult to prove.”

Deficiencies of certain nutrients can be harmful; in some cases, an excess can also be bad. In two separate studies, smokers who were given high doses of beta carotene—a naturally occurring compound that converts in the body to vitamin A, and which is thought to be protective against cancer—unexpectedly developed more lung cancers than smokers who were on placebos. The high doses caused DNA damage instead of blocking the cancer as intended, according to Marji McCullough, a nutritional epidemiologist with the American Cancer Society.

Generally speaking, Joel Mason, professor of medicine and nutrition at Tufts, argues for a middle path. Like some medications, certain nutrients and vitamins may need to be delivered within an optimal range to confer benefit, he says. He and others in the field have labeled this concept the “Goldilocks phenomenon.”